There is no doubt that there is a need to think differently about how surface water is managed if flooding is not to be a persistent problem. A structured approach to this problem is outlined in this presentation.

2. There is no doubt that
there is a need to think
differently about how
surface water is managed
if flooding is not to be a
persistent problem.

3. Flood Risk Areas
South Essex
West Midlands
Leicester
Hull
Greater Manchester
Liverpool
Bristol
Brighton & Hove
London
Medway

4. SWMP Guidance 2010
“A SWMP should establish a long-term action plan
to manage surface water in an area and should
influence future capital investment, drainage
maintenance, public engagement and
understanding, land use planning, emergency
planning and future developments”
Many LLFA’s have completed SWMP’s up
to “Risk Assessment” stage or beyond.

5.  A straight forward approach (already being
adopted by a number of Water & Sewerage
Companies) has the potential for widespread
adoption as it is very user friendly.
 The approach is :
 Sequential
 Transparent
 Easily Understood
 Identifies the best cost benefit solutions

6. Flow Reduction
Diversion
Storage
Exceedance
Protection
Conveyance

7. FlowReduction
Conveyance
Increasing Cost
IncreasingBenefits

8. Flow Reduction
Diversion
Storage
Exceedance
Protection
Conveyance
 First preference to establish whether the
flows can be reduced
– Suds
– Infiltration
– Green Roofs
– Separation
– Source Control
– Rainwater Gardens

9. Areas which could be Permeable Pavements

10. Existing flat roofs which
could be ‘Green Roofs’

11. Excessively wide footpaths
which could be reduced

12. Chevron
areas
could be
gravel

14. Limit flows
entering
drainage
systems
Maximise
capacity of
the drainage
system
Manage
flows above
ground
Improve
resilienc
e
Surface
water used
as a
resource
Surface water
used as an
amenity
Improve
water
quality
Increase
extent and
viability of
green
infrastructure

16.  Especially where pluvial runoff from rural
outskirts flows in to urban areas
 Flows have to be diverted to a safe area
 Often used in conjunction with storage
solutions
Flow Reduction
Diversion
Storage
Exceedance
Protection
Conveyance

17. Diversion
channel

23.  Particularly cost effective option
 Usually above ground storage, in
fields or parkland either within or
upstream of urban areas.
 Important to consider size, height and
visual impact
Flow Reduction
Diversion
Storage
Exceedance
Protection
Conveyance

24. Rainwater Butts
Rainwater Harvesting

25.  Enhancing existing flood pathways to
become more formal exceedance routes
 May need measures to ensure that the
water stays within the pathway;
 Continuous kerbs
 Profiling roads
Flow Reduction
Diversion
Storage
Exceedance
Protection
Conveyance
Exceedance is flow that is conveyed or stored on the surface because the capacity
of a drainage system carrying storm water (including as a result of a blockage to
an inlet) has been exceeded

30. Note how footpaths and drives fall
away from kerb towards houses

31.  Conducted at property level
 Generally only individual or small number
of properties benefited
 Relatively expensive
Flow Reduction
Diversion
Storage
Exceedance
Protection
Conveyance

32. Traditional external
flood barriers
Modern range of
Watertight doors

33.  Upsizing sewers / widening or deepening
river channels
 Reduces the time for water to pass through
parts of the catchment
 Can cause issues downstream
 Existing channels can be altered to increase
capacity
Flow Reduction
Diversion
Storage
Exceedance
Protection
Conveyance

34.  Structured approach allows for comparison of
measures on a variety of criteria
 Avoids an instinctive response towards
selecting certain types of measure for cost
 Conveyance measures such as upsizing
sewers & widening/deepening river channels
have their place but are not the only option
 There is a hierarchy of other possible
solutions

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